Chemical carcinogens

Question 1

what is 3,4-benzypyrene oxidised by and to

Answer 1

glutathione s-transferases to 7,8-epoxide metabolite

Question 2

where is p53 highly active

Answer 2

malignant cells

Question 3

what does error-prone DNA replication require

Answer 3

DNA polymerases delta and epsilon

Question 4

Which cytochromes biotransforms polycyclic aromatic hydrocarbons (4)

Answer 4

1. P450
2. 1A1
3. 1A2
4. 1B1

Question 5

what is the formation of epoxides catalysed by

Answer 5

UDP-dependent glycuronosyl transferases

Question 6

what is the chemically structure of polycyclic aromatic hydrocarbons

Answer 6

carbon and hydrogen arranged into aromatic rings

Question 7

what do all major carcinogens in this group contain

Answer 7

bay region

Question 8

what does the K region contain

Answer 8

higher electron density

Question 9

what is a imbalance between K and L regions suggested to cause

Answer 9

carcinogenicity

Question 10

what can epoxides form

Answer 10

K regions

Question 11

what occurs during nucleotide excision repair

Answer 11

repairing of DNA damage with low fidelity

Question 12

where are polycyclic aromatic hydrocarbons in the environment from

Answer 12

anthropogenic sources

Question 13

where is the aryl hydrocarbon receptor found

Answer 13

nucleus of hepatocytes

Question 14

what excretes polycyclic aromatic hydrocarbons

Answer 14

kidneys

Question 15

what do the bay regions bind with in particular

Answer 15

NH2 group of guanine

Question 16

what kind of molecules are PAHs

Answer 16

planar molecules

Question 17

what do most PAHs contain

Answer 17

phenanthrene nucleus

Question 18

where in the plenanthrene moiety is the bay region located

Answer 18

C4 to C6

Question 19

what increases carcinogenicity

Answer 19

addition of other planar ring systems to C6C7

Question 20

two types of cancer

Answer 20

benign and malignant

Question 21

three most common classifications of cancer and where do they develop

Answer 21

1. carcinomas - epithelial cells
2. sarcomas - bone and muscle
3. leukaemia - blood

Question 22

five classes of chemical carcinogens

Answer 22

1. alkylating agents
2. nitroso compounds
3. azo dyes
4. aromatic amines
5. polycyclic aromatic hydrocarbons (PAHs)

Question 23

when are PAHs generated

Answer 23

whenever organic materials are burned

Question 24

when was the association between cancer and PAHs first noted

Answer 24

in 1775

Question 25

what do the diol-epoxides of 3,4-benzypyrene normally bind to?

Answer 25

guanine residues of DNA

Question 26

what correlations were found between carcinogenic activity and electron density

Answer 26

high electron density resulted in greater carcinogenic activity

Question 27

what do PAHs form and what is this reaction catalysed by?

Answer 27

K-region epoxides catalysed by cytochrome p450

Question 28

why are epoxides dangerous?

Answer 28

they react directly with DNA forming mutagens and carcinogenic activity

Question 29

what became clear by the 1970s regarding epoxides

Answer 29

that non-K-region exoxides could exist

Question 30

how do the diol-epixodes of 3,4-benzpryene bind to guanine

Answer 30

covalent bond is formed between C10 of benzo(a)pyrene and the exocyclic 2-amino

Question 31

why does binding of PAH cause damage to DNA

Answer 31

repair is not always accurate leading to point mutations

Question 32

what do 10% of human tumours contain

Answer 32

mutations of ras genes

Question 33

what is different about oncogenic p21

Answer 33

it has lost its GTPase activity = constant signalling for growth

Question 34

how to measure PAH exposure

Answer 34

electrophilic metabolites of PAHs form covalent adducts with albumin and haemoglobin which can then be assayed